There are people who do not believe the theory of evolution is sufficient to explain the existence of the world as we know it. They prefer to believe in creationism, the idea that there is a deity who created the world. I have no problem with people who wish to believe this, it is their prerogative, of course, just as they may chose to believe the Sun orbits the Earth, or that the Earth is 6,000 years old.

Because the belief systems of organized religions like Christianity are thousands of years old they predate a great deal of scientific learning, and there are situations where religious dogma contradicts current knowledge. Some of these conflicts have been resolved over time; very few religious people still believe the Sun orbits the Earth, for example, although as recently as 1633 Galileo was condemned for heresy because he proved otherwise. Today most religious people accept that the Earth is billions of years old, based on overwhelming geologic evidence. However many religious people still reject evolution as an accepted scientific theory, despite the strong evidence in its favor, and despite the fact that few scientists have doubts about its validity.

Note: one may accept evolution as a scientific theory and still be a creationist. Evolution does not say anything about the existence of a deity, it says only that the existence of a deity is not necessary to explain the world.

People who are anti-evolution try to position creationism as an alternative to evolution, but they are different things entirely. Evolution is a scientific theory, which attempts to explain observed facts and makes predictions, while creationism is a human belief, sustained by faith. Be that as it may, creationists nonetheless have invented terms like "creation science" and "intelligent design" to position their beliefs as a theory. In some sense they feel their beliefs are competitive with evolution, as if the two were mutually exclusive.

Note: there are known facts which are not fully explained by current theories of evolution. These facts do not mean "evolution is wrong"; as with any scientific theory, evolution steadily evolves to explain more and more observed facts. Apparent contradictions between facts and evolution provide no evidence at all for creationism.

Advocates of intelligent design have been working hard to convince public school systems to modify their science curricula to teach intelligent design alongside evolution. Aside from the confusion between religion and science, this is simply unintelligent; we don't teach our kids the theory that the Sun orbits the Earth, nor that the Earth is 6,000 years old. These efforts have mostly failed to gain traction, but simply raising the issue in debate has value to creationists, because some people assume "where there's smoke, there's fire".

Recently I had an interesting email exchange with a reader who asked good questions about evolution and creationism. I've copied his questions and my answers below:

1. How did life begin? How did the first cells evolve from nonliving matter? Have we ever seen life produced from non-life in a laboratory?

Life began incrementally, from crystals which were self-replicating. Over time the crystals accumulated “mutations” which improved either their fidelity of replication, or their fecundity (rate). Such mutations were selected for and became predominant. Slowly component specialization crept in. There are many books which tell this story in detail – the chemistry is well characterized. The key here is that there was no moment at which life suddenly started. Life is a meta-property of matter configurations.

Scientists have been able to form complex organic molecules like amino acids in labs by duplicating the conditions found in the first billions of years on Earth. They have not made life, of course, because they haven’t had enough time!

2. How can genetic mutations bring about drastically different life forms? For example, when reptiles evolved into birds, they supposedly grew wings. That means there must be intermediate creatures with half-wings. But a half-wing is not an advantage that is naturally selected for, it is a big disadvantage! So how did the wing ever evolve? Have we ever seen one species mutate into another species in a laboratory?

Speciation is exactly like life – there is no one moment where suddenly you have a new species, any more than there is one moment when you have life. Gradual mutations are responsible for all the incredible variation we see in life today. Richard Dawkins’ book Climbing Mount Improbable is a great discussion of this objection, and contains a specific discussion of the evolution of wings. It turns out a half-wing does have advantage. Eyes are another commonly cited “thing which couldn’t have evolved”. But half-eyes existed - they exist today, in fact - and eyes evolved not once but at least seven different times.

3. Why doesn't the fossil record show any evidence of intermediate species? To my knowledge, there is not a single example of an intermediate species, even though the earth's crust should be full of such fossils. Have we ever found a single example of an intermediate species in which we are confident?

There’s no such thing as intermediate species. Species evolve gradually and later you can look back and note that speciation apparently occurred over some timescale. The fossil record is amazing – it shows a huge variety of different species including entire phyla which are no longer in existence, victims of natural selection.

One way to think about this is to consider the common objection that “humans can’t be descended from apes”. Well, no. Humans and apes have common ancestors, but at the time those ancestors lived neither humans nor chimpanzees were in existence.

4. These flaws are really big! They all suggest that each species was created by an intelligent creator with a specific purpose. I cannot imagine a reasonable alternative to the theory of evolution, but it looks like I might have to.

Assuming you don't accept my explanations of these "flaws", nor anyone else's, they provide no evidence at all for creationism. Flaws in evolution mean improvements in the theory are needed. Creationism is simply giving up; if you can't explain something scientifically, postulate magic.

To me a belief in magic is far worse than a belief in science. I can’t imagine there really could be such a thing as an intelligent creator. Explaining that would be much harder than explaining any of the things which such an intelligent creator might have created. (Who created the creator?) The argument for intelligent design is appealing to people who feel evolution defies their intuition. It doesn’t solve the problem, but it is comfortable.

Obviously religious belief is personal, and I have no problem with anyone who doesn’t believe as I do. I only ask that they admit they are choosing to believe in “magic” instead of rational facts and logical reasoning.

Finally, I must caution those thinking about these issues not to invoke the “argument from incredulity”. Many people feel evolution violates their common sense, and so it can’t be right. People have the same reaction to other science – relativity, or quantum mechanics, or the scale of the universe. The big disconnect is time; evolution on Earth has been quietly operating for billions of years, far longer than anything we can easily grasp.

If you are interested in these issues I recommend Daniel Dennett’s classic book Darwin’s Dangerous Idea. It deals with all these issues and many others in a wonderful entertaining way.